The Post-tensioned Mat Slab is derived from criteria presented in UBC
1816 by incorporating the design output of the Ribbed Slab (PTI) and
equating its calculated moment of inertia into an equivalent thick
post-tensioned mat. Some have no perimeter beams other than just a
turned down edge to penetrate the grade. Other applications can
incorporate an deepened exterior beam to provide a moisture cutoff wall
while increasing edge rigidity.
Illustrated is a mat slab prior to concrete
Interior stiffening beams are generally
not used however thickened sections may occur to provide anchor bolt
and/or hold down clearance where necessary. Design criteria is the
same as that required for the ribbed slab; ie. anticipated soil movement.